Pectin, a long-chain molecule present in plant cell walls, was found to provide a similar electrical response to temperature changes, so a team from Caltech and ETH Zurich went to work.

Mixing pectin with water, the engineers built a thin, transparent and flexible film to act like skin – they claim it works even when just 20 micrometers thick.

“Pectin is widely used in the food industry as a jellifying agent. It’s what you use to make jam. So it’s easy to obtain and also very cheap,” said Chiara Daraio, a professor at Caltech who led the study, which will be published in Science Robotics in February.

Pectin molecules in the film have a weakly bonded double-strand structure that contains calcium ions, which break down as temperatures rise. This leads to easily detected charged ions and is how it ‘feels’ heat.

The evolution of digital skin has been remarkable in the past two years. In 2015, scientists developed a ‘skin-inspired organic digital mechanoreceptor’ that could give people with prosthetic limbs a type of feeling that is otherwise, obviously, lacking.

By March last year, a flexible, stretchable, even tuneable, ‘meta-skin’ was developed by US researchers – a wearable skin for aircraft that acts as a type of ‘invisibility cloak’.

Within weeks of that discovery, tiny, micropower, nano-batteries were created to support e-skin structures on the human body, before a team of researchers from the University of Tokyo developed an ultra-thin and ultra-flexible wearable display.

A more adaptive skin was then developed in the US, providing a stretchable option, utilizing 5G technology.

Now, with temperature management a possibility, a true digital skin is closer to reality.